1. Field of Invention
This invention concerns sulfur-containing carbonate reaction products and their use as antiwear additives in lubricating oils, particularly automatic transmission fluids.
2. Description of Related Art
Additives for lubricating oils perform an important role in tailoring a finished fluid to meet specific performance criteria set by equipment manufacturers. Typically, wear of moving equipment parts is controlled by phosphorus-containing compounds. However, these compounds may adversely affect other characteristics desirous in lubricating oils such as friction performance and silicone-seal compatibility. Therefore, under certain circumstances, it may be advantageous to avoid use of phosphorus-containing compounds. Additionally, there is a continuing search for new antiwear additives which are inexpensive to produce and, environmentally benign, and compatible with conventional lubrication oil additives. The additives of this invention offer one response to these problems.
GB 1,353,249 discloses that carbonic acid esters of the following formula are useful lubricants and lubricant additives: ##STR1## where: R.sup.1 and R.sup.2 are independently a hydrogen atom, or an alkyl, alkenyl, aralkyl, aryl, acyl, alkoxy-carbonyl or aryloxy-carbonyl group;
n is a number from 2 to 300; and PA1 X is an alkylene radical which contains 3 or more, preferably 3 to 18 carbon atoms in the main chain, an alkylene radical which contains 3 or more, preferably 3 to 18 carbon atoms in the main chain and is interrupted by one or more heteroatoms or by one or more carboxylic ester, carbamoyl, urethane, urea or tertiary amino groups; or PA1 X is a cycloalkylene, aralkylene or arylene radical. PA1 m is O or an integer from 1 to 4; PA1 n is O or an integer from 1 to 4; PA1 q is O or an integer from 1 to 6; PA1 R is a C.sub.1 -C.sub.50 hydrocarbyl group in structure (I), and is a C.sub.1 -C.sub.50 hydrocarbyl group or hydrogen in structure (II); PA1 X is sulfur, oxygen, nitrogen, or --CH.sub.2 --; PA1 r is O, or an integer from 1 to 5 providing when X is oxygen or nitrogen, r is 1, when X is sulfur, r is 1 to 3, when X is --CH.sub.2 --, r is 1 to 5; PA1 s is O, or an integer from 1 to 5; PA1 t is O, or an integer from 1 to 12; PA1 u is O, or an integer from 1 to 2 providing when X is sulfur, oxygen, or --CH.sub.2 --, u is 1, when X is nitrogen, u is 1 or 2; PA1 y is O, or an integer from 1 to 10; and PA1 R.sub.1 and R.sub.2 are independently a C.sub.1 -C.sub.6 alkyl, cycloalkyl, aryl, C.sub.1 -C.sub.6 alkyl-substituted aryl, or hydrogen. PA1 r is 1 to 3; PA1 R.sub.1, and R.sub.2 are independently hydrogen, C.sub.1 -C.sub.6 alkyl, cycloalkyl, aryl, or C.sub.1 -C.sub.6 alkyl-substituted aryl; PA1 s is an integer from 1 to 5; and ##STR4##
The heteroatoms described include oxygen, sulfur, and nitrogen. However, since n=2, the claimed carbonic acid esters contain at least 2 carbonate radicals formed by alcohol exchange reactions using diols. Additionally, there is nothing in this reference to suggest the lubricating oil additives of this invention.